﻿using System;

namespace SanlieHash.BlockCipher
{
    public class AES : ICrypto
    {
        internal byte[] _Key;
        internal byte[] _Keys;
        internal int _Nr;
        internal byte[] _Input;

        /// <summary>
        /// AES class contructor.
        /// </summary>
        /// <param name="securityKey">
        /// The key will be used in encrypting and decrypting the input.
        /// </param>
        public AES(byte[] securityKey = null)
        {
            SetPassword(securityKey);
        }
        public AES(string securityKey)
        {
            ExpandingKey.Process(System.Text.Encoding.Unicode.GetBytes(securityKey), out _Nr, out _Key, out _Keys);
        }
        public AES()
        {
        }
        public void SetPassword(byte[] password)
        {
            ExpandingKey.Process(password, out _Nr, out _Key, out _Keys);
        }

        /// <summary>
        /// This function will encrypt array of bytes.
        /// </summary>
        /// <param name="byteInput"></param>
        /// <returns>
        /// Encrypted array of bytes.
        /// </returns>
        public byte[] Encrypt(byte[] byteInput)
        {
            if (byteInput == null || byteInput.Length <= 0)
            {
                throw new ArgumentException("No input", nameof(byteInput));
            }

            try
            {
                _Input = new byte[byteInput.Length+1];
                byteInput.CopyTo(_Input, 0);
                _Input[byteInput.Length] = 255;
                return ProcessEncrypt();
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }

        /// <summary>
        /// Static function to execute array of bytes encryption.
        /// </summary>
        /// <param name="encryptKey">Key string that used to encrypt the array of bytes.</param>
        /// <param name="byteInput"></param>
        /// <returns>
        /// Encrypted array of bytes.
        /// </returns>
        public static byte[] EncryptBytes(string encryptKey, byte[] byteInput)
        {
            using (AES aes = new AES(encryptKey))
            {
                return aes.Encrypt(byteInput);
            }
        }
        /// <summary>
        /// Decrypt array of bytes.
        /// </summary>
        /// <param name="byteInput"></param>
        /// <returns>
        /// Decrypted array of bytes.
        /// </returns>
        public byte[] Decrypt(byte[] byteInput)
        {
            if (byteInput == null || byteInput.Length <= 0)
            {
                throw new ArgumentException("No input", nameof(byteInput));
            }

            try
            {
                _Input = new byte[byteInput.Length];
                byteInput.CopyTo(_Input, 0);
                byte[] decrypted = ProcessDecrypt();
                if (decrypted == null || decrypted.Length <= 0) return null;

                var i = 0;

                for(i = decrypted.Length-1; i>=0; i--)
                {
                    if (decrypted[i] == 255)
                    {
                        break;
                    }
                }
                Array.Resize(ref decrypted, i);
                return decrypted;
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }
        /// <summary>
        /// Static function to execute the decryption of array of byte.
        /// </summary>
        /// <param name="decryptKey"></param>
        /// <param name="byteInput"></param>
        /// <returns>
        /// Decrypted array of bytes.
        /// </returns>
        public static byte[] DecryptBytes(string decryptKey, byte[] byteInput)
        {
            using (AES aes = new AES(decryptKey))
            {
                return aes.Decrypt(byteInput);
            }
        }

        public byte[] ProcessDecrypt()
        {
            byte[] BlockIn = new byte[Common.maxKeyLength];
            byte[] BlockOut;
            byte[] Output = new byte[_Input.Length +
                ((_Input.Length % Common.maxKeyLength) == 0 ? 0 :
                (Common.maxKeyLength - (_Input.Length % Common.maxKeyLength)))];
            int Temp = _Input.Length / Common.maxKeyLength;
            for (int i = 0; i < Temp; i++)
            {
                Array.Copy(_Input, i * Common.maxKeyLength, BlockIn, 0, Common.maxKeyLength);
                BlockOut = DecryptingLoop(BlockIn);
                Array.Copy(BlockOut, 0, Output, i * Common.maxKeyLength, Common.maxKeyLength);
            }
            int lastByte = _Input.Length % Common.maxKeyLength;
            if (lastByte > 0)
            {
                BlockIn = new byte[Common.maxKeyLength];
                Array.Copy(_Input, _Input.Length - lastByte, BlockIn, 0, lastByte);
                BlockOut = DecryptingLoop(BlockIn);
                Array.Copy(BlockOut, 0, Output,
                    Output.Length - Common.maxKeyLength, Common.maxKeyLength);
            }
            return Output;
        }
        internal byte[] DecryptingLoop(byte[] block)
        {
            Common.AddRoundKey(block, _Keys, _Nr);
            for (int i = _Nr - 1; i > 0; i--)
            {
                InverseShiftRows(block);
                InverseSubBytes(block);
                Common.AddRoundKey(block, _Keys, i);
                InverseMixColumns(block);
            }
            InverseShiftRows(block);
            InverseSubBytes(block);
            Common.AddRoundKey(block, _Keys, 0);
            return block;
        }
        internal void InverseSubBytes(byte[] block)
        {
            for (int i = 0; i < Common.maxKeyLength; i++)
                block[i] = Common.ISBox[block[i]];
        }

        internal void InverseShiftRows(byte[] block)
        {
            byte[] temp = new byte[4];
            for (int i = 1; i < 4; i++)
            {
                for (int j = 0; j < 4; j++)
                    temp[(i + j) % 4] = block[(i * 4) + j];
                for (int j = 0; j < 4; j++)
                    block[(i * 4) + j] = temp[j];
            }
        }
        internal void InverseMixColumns(byte[] block)
        {
            byte[,] t = new byte[4, 4];
            for (int i = 0; i < 4; i++)
            {
                for (int j = 0; j < 4; j++)
                {
                    t[i, j] = block[i * 4 + j];
                }
            }
            for (int i = 0; i < 4; i++)
            {
                block[00 + i] = (byte)(PeasantMultiplication.Calculate(14, t[0, i]) ^
                    PeasantMultiplication.Calculate(11, t[1, i]) ^
                    PeasantMultiplication.Calculate(13, t[2, i]) ^
                    PeasantMultiplication.Calculate(9, t[3, i]));
                block[04 + i] = (byte)(PeasantMultiplication.Calculate(9, t[0, i]) ^
                    PeasantMultiplication.Calculate(14, t[1, i]) ^
                    PeasantMultiplication.Calculate(11, t[2, i]) ^
                    PeasantMultiplication.Calculate(13, t[3, i]));
                block[08 + i] = (byte)(PeasantMultiplication.Calculate(13, t[0, i]) ^
                    PeasantMultiplication.Calculate(9, t[1, i]) ^
                    PeasantMultiplication.Calculate(14, t[2, i]) ^
                    PeasantMultiplication.Calculate(11, t[3, i]));
                block[12 + i] = (byte)(PeasantMultiplication.Calculate(11, t[0, i]) ^
                    PeasantMultiplication.Calculate(13, t[1, i]) ^
                    PeasantMultiplication.Calculate(9, t[2, i]) ^
                    PeasantMultiplication.Calculate(14, t[3, i]));
            }
        }
        public byte[] ProcessEncrypt()
        {
            byte[] BlockIn = new byte[Common.maxKeyLength];
            byte[] BlockOut;
            byte[] Output = new byte[_Input.Length +
                ((_Input.Length % Common.maxKeyLength) == 0 ? 0 :
                (Common.maxKeyLength - (_Input.Length % Common.maxKeyLength)))];
            int tmp = _Input.Length / Common.maxKeyLength;
            for (int i = 0; i < tmp; i++)
            {
                Array.Copy(_Input, i * Common.maxKeyLength, BlockIn, 0, Common.maxKeyLength);
                BlockOut = EncryptingLoop(BlockIn);
                Array.Copy(BlockOut, 0, Output, i * Common.maxKeyLength, Common.maxKeyLength);
            }
            int lastByte = _Input.Length % Common.maxKeyLength;
            if (lastByte > 0)
            {
                BlockIn = new byte[Common.maxKeyLength];
                Array.Copy(_Input, _Input.Length - lastByte, BlockIn, 0, lastByte);
                BlockOut = EncryptingLoop(BlockIn);
                Array.Copy(BlockOut, 0, Output,
                    Output.Length - Common.maxKeyLength, Common.maxKeyLength);
            }
            return Output;
        }
        internal byte[] EncryptingLoop(byte[] block)
        {
            Common.AddRoundKey(block, _Keys, 0);
            for (int i = 1; i < _Nr; i++)
            {
                SubBytes(block);
                ShiftRows(block);
                MixColumns(block);
                Common.AddRoundKey(block, _Keys, i);
            }
            SubBytes(block);
            ShiftRows(block);
            Common.AddRoundKey(block, _Keys, _Nr);
            return block;
        }
        internal void SubBytes(byte[] block)
        {
            for (int i = 0; i < Common.maxKeyLength; i++)
                block[i] = Common.SBox[block[i]];
        }
        internal void ShiftRows(byte[] block)
        {
            byte[] temp = new byte[4];
            for (int i = 1; i < 4; i++)
            {
                for (int j = 0; j < 4; j++)
                    temp[j] = block[(i * 4) + ((i + j) % 4)];

                for (int j = 0; j < 4; j++)
                    block[(i * 4) + j] = temp[j];
            }
        }
        internal void MixColumns(byte[] block)
        {
            byte[,] t = new byte[4, 4];
            for (int i = 0; i < 4; i++)
                for (int j = 0; j < 4; j++)
                    t[i, j] = block[i * 4 + j];

            for (int i = 0; i < 4; i++)
            {
                block[00 + i] = (byte)(PeasantMultiplication.Calculate(2, t[0, i]) ^
                    PeasantMultiplication.Calculate(3, t[1, i]) ^ t[2, i] ^ t[3, i]);
                block[04 + i] = (byte)(t[0, i] ^ PeasantMultiplication.Calculate(2, t[1, i]) ^
                    PeasantMultiplication.Calculate(3, t[2, i]) ^ t[3, i]);
                block[08 + i] = (byte)(t[0, i] ^ t[1, i] ^ PeasantMultiplication.Calculate(2, t[2, i]) ^
                    PeasantMultiplication.Calculate(3, t[3, i]));
                block[12 + i] = (byte)(PeasantMultiplication.Calculate(3, t[0, i]) ^ t[1, i] ^ t[2, i] ^
                    PeasantMultiplication.Calculate(2, t[3, i]));
            }
        }
        
        /// <summary>
        /// Disposing AES object.
        /// </summary>
        public void Dispose()
        {
            _Input = _Key = _Keys = null;
            GC.Collect();
        }

        internal static class PeasantMultiplication
        {
            public static int Calculate(int a, int b)
            {
                int aa = a, bb = b, r = 0, t;
                while (aa != 0)
                {
                    if ((aa & 1) != 0)
                        r ^= bb;
                    t = bb & 0x80;
                    bb <<= 1;
                    if (t != 0)
                        bb ^= 0x1b;
                    aa >>= 1;
                }
                return r;
            }
        }
        internal class Common
        {
            internal static int maxKeyLength = 16;

            internal static void AddRoundKey(byte[] block, byte[] keys, int round)
            {
                for (int i = 0; i < 16; i++)
                    block[i] = (byte)(block[i] ^ keys[round * 4 + i]);
            }

            private static byte[] _Round;
            internal static byte[] Round
            {
                get
                {
                    if (_Round == null)
                        _Round = new byte[11] { 0x00, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36 };
                    return _Round;
                }
            }

            private static byte[] _SBox;
            internal static byte[] SBox
            {
                get
                {
                    if (_SBox == null)
                        _SBox = new byte[16 * 16] {
                        0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
                        0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
                        0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
                        0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
                        0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
                        0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
                        0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
                        0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
                        0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
                        0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
                        0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
                        0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
                        0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
                        0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
                        0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
                        0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
                    };

                    return _SBox;
                }
            }

            private static byte[] _ISBox;
            internal static byte[] ISBox
            {
                get
                {
                    if (_ISBox == null)
                        _ISBox = new byte[16 * 16] {
                        0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
                        0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
                        0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
                        0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
                        0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
                        0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
                        0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
                        0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
                        0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
                        0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
                        0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
                        0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
                        0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
                        0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
                        0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
                        0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d
                    };

                    return _ISBox;
                }
            }
        }
        internal class ExpandingKey
        {
            private static byte[] NormalizeKey(byte[] key)
            {
                var keylen = key == null ? 0: key.Length;
                var max = Common.maxKeyLength <<1;
                if (keylen == 0)
                {
                    key = new byte[max];
                    for (int i = 0; i < max; i++) key[i] = 0;
                }
                else if (keylen > max)
                {
                    Array.Resize(ref key, max);
                }
                else if (keylen < max)
                {
                    Array.Resize(ref key, max);

                    for (int i = keylen, j = 0; i < max; i++)
                    {
                        key[i] = key[j++];
                        if (j == keylen) j = 0;
                    }
                }
                return key;
            }

            public static void Process(byte[] key, out int nr, out byte[] bKey, out byte[] bKeys)
            {
                key = NormalizeKey(key);
                int Nk = key.Length / 2;
                nr = Nk + 6;
                bKey = new byte[key.Length * 4];
                bKeys = new byte[4 * 4 * (nr + 1)];
                key.CopyTo(bKey, 0);
                bKey.CopyTo(bKeys, 0);
                byte[] temp = new byte[4];
                for (int i = Nk; i < 4 * (nr + 1); i++)
                {
                    for (int j = 0; j < 4; j++)
                        temp[j] = bKeys[(i - 1) * 4 + j];

                    if (i % Nk == 0)
                    {
                        temp = SubWord(RotWord(temp));
                        temp[0] = (byte)(temp[0] ^ Common.Round[i / Nk]);
                    }
                    else if (Nk > 6 && (i % Nk == 4))
                        temp = SubWord(temp);

                    for (int j = 0; j < 4; j++)
                        bKeys[i * 4 + j] = (byte)(bKeys[(i - Nk) * 4 + j] ^ temp[j]);
                }
            }

            private static byte[] SubWord(byte[] input)
            {
                return new byte[4]{
                    Common.SBox[input[0]],
                    Common.SBox[input[1]],
                    Common.SBox[input[2]],
                    Common.SBox[input[3]]
                };
            }

            private static byte[] RotWord(byte[] input)
            {
                return new byte[4] {
                input[1],
                input[2],
                input[3],
                input[0]
            };
            }
        }
    }
}
